Feed dog recutting fixture



Feb. 18, 1936..

L. C. CORCORAN FEED DOG RECUTTING FIXTURE Filed June 18, 1935 INVENTOR.ofeonarc/ C Carwmrz Patented Feb. 18, 1936 UNITED STATES PATENT OFFICEFEED DOG RECUTTING FIXTURE Leonard C. Corcoran, ClevelandHeights, OhioApplication June 18, 1935, Serial No. 27,218

4Claim5. (c1. 29-46) The present invention relates to afixture forrecutting, reservicing, and salvaging used sewing machine feed dogs. Thegeneral object and nature of my invention is to provide a device adaptedto hold all sizes, shapes and types of sewing machine feed dogs,together with means for guiding a recutting tool, such a's-a file,whereby the damaged and worn teeth of such feed dogs may be accuratelyand quickly recut and placed in a serviceable condition. 7

A further object of the invention is to provide such a feed dogrecutting fixture which is of simplified construction and of a portablenature whereby the fixture can be carried about in the repair mans toolbox and clamped in an ordinary bench vise during use. Additional objectsand advantages of the invention shall become apparent as the followingdescription proceeds. To the accomplishment of the foregoing and relatedends, said invention, then, consists of the means hereinafter fullydescribed and particularly pointed out in the claims.

The annexed drawing and the following description set forth in detailcertain mechanism embodying the invention, such disclosed meansconstituting, however, but one of various mechanical forms in which theprinciple of the invention may be used.

In said annexed drawing:

Fig. 1 is a perspective view of the fixture embodying the principle ofmy invention; Fig. 2 is a top plan view of the device shown in Fig. 1;Fig. 3 is a side elevational view partially in section, the sectionedportion being taken substantially along the line 33 of Fig. 2; and Fig.4 is a perspective view of a legless type of feed dog adapted to beserviced by my fixture.

Since a feed dog is an element of a sewing machine which is particularlysubject to damage and wear, due to the fact that it grips and releasesthe material being sewed each time a stitch is taken, it is of utmostimportance that the grippingteeth of such a feed dog be maintained in anefficient and serviceable condition. The efiiciency of operation of theentire sewing machine mechanism is dependent upon the ability of thefeed dog to properly grip and advance the material at each stitch. Thefixture of my invention which has been designed for the purpose ofrecutting and maintaining the proper condition of sewing machine feeddog teeth, consists essentially of a pair of guides for supporting thereciprocal movement of a cutting tool such as a triangular file, and awork holding block movable with respect to such guides whereby theposition of. a feed dog carried by such block may be adjusted and thecutting operation may be properly aligned and gauged.

Referring more particularly to the drawing, my fixture consists of arectangular base block 5 I having parallel sides 2 whereby the fixturemay be clamped and held in an ordinary bench vise (not shown). Fourposts 3 positioned adjacent the four corners of the base block I carrythe hardened steel bars or file guides 4. A work 10 holding block 5 ismovably supported with respect to the base block I by means of the twopins 6 fixed to the block 5 and slidable through holes'drilled in thebase block I. The pins 6 serve 'as means for maintaining and accuratelyguiding the movable block 5 with respect to the base block I and thefile guides 4. A threaded shaft I threadably engages the base block I asat 8 and is locked against longitudinal movement in the work holdingblock 5 by means of the pointed set screw 9 whose end engages in aV-shaped annular groove in the end of the threaded shaft I. A winghandle I I is fixedto the outer end of the shaft I and serves 'as meansfor facilitating the manual rotation thereof. A wing nut I I' threadablyengages the shaft I and is adapted to bear against thebottom side of thebase block I for locking the shaft 1 against rotation and therebyholding the movable work holding block 5 in desired position.

A feed dog I5 of the projecting leg type, and having a series of teethI6 is adapted to be mounted upon the work holding block 5. Such mountingis accomplished by means of a slot or channel H in the side face of theblock 5, in which the leg I8 of the feed dog I5 closely fits. A stud I9passes through the opening in the feed dog leg I8 and threadably engagesthe tapped hole 2I in the work holding block 5. Additional slots ofwider dimensions, such as the slot II may be provided in order toaccommodate feed dogs having legs of different widths.

Legless feed dogs such as the feed dog shown in Fig. 4 are mounted onthe top surface of the work holding block 5 by means of suitable screwsor studs passing through the holes 26 in the feed dog and engaged in thetapped holes 21 in the block 5. A triangular file 30 having rounded ends3| and 32 constitutes the cutting tool. The end portions ill and 32 ofthe file are adapted to bear against and be guided by the parallel guidebars 4. The intermediate portion of the file 30 bears against thesurfaces of the feed dog teeth I6 (as best shown in Fig. 3) and recutsthem to accurate and desired form.

In operation, the damaged feed dog is removed from the sewing machine,annealed in order to soften the metal therein, mounted upon the workholding block 5 and the latter is adjusted to such a position withrespect to the file guides 4 where'- by the necessary depth of cut willresult. The alignment and uniformity of the recutting oper ation of thefeed dog teeth l6 may be inspected and checked from time to time bymoving the block l5 and sighting across the top of the parallel fileguides 4. After the recutting operation, the feed dog may be reinstatedto its previous case hardened condition by a simple cyanide bathtreatment.

The above described fixture permits the recutting and salvaging ofdamaged and worn sewing machine feed dogs which heretofore have beencompletely discarded and replaced by new ones. The fixture may beconveniently carried about from place to place by the repair man, andeasily mounted in an ordinary vise, or can even be held by hand. It willalso be seen that my abovedescribed fixture is of universal application,and will accommodate practically all sizes, types and shapes of sewingmachine feed dogs.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a sewing machine feed dog recutting fixture, the combination of abase block having parallel side faces adapted to be gripped by anordinary vise, file guides carried in spaced relationship with respectto said block, and a work holding block movable with respect to saidguides, said work holding block having a fiat upper surface for theattachment of legless feed dogs, and

also having slots in its side faces for the attachment of feed dogs withextending legs.

2. In a sewing machine feed dog recutting fixture, the combination of abase block having parallel side faces adapted to be gripped by anordinary vise, parallel hardened bars carried in spaced relationshipwith respect to said block, said bars being adapted to guide thereciprocal movement of a filing tool, a work holding block adapted tohold feed dogs in a position with their teeth parallel to said guides,said work holding block having a flat upper surface for the attachmentof legless feed dogs and also having slots in its side faces for theattachment of feed dogs with extending legs, a rotatable shaft locatedto said work holding block and threadably engaging said base block, anda lock nut on said shaft for locking the latter against rotation to saidbase block.

3. In a sewing machine feed dog recutting fixture, the combination of abase block having parallel side faces adapted to be gripped by anordinary vise, file guides carried in spaced relationship with respectto said block, a work hold ing block movable with respect to saidguides, said work holding block being adapted to hold feed dogs in aposition with their teeth parallel to said guide, and guide pins carriedby said work holding block and slidably positioned in said base block.

4. In a sewing machine feed dog recutting fixture, the combination of abase block having parallel side faces adapted to be gripped by anordinary vise, parallel hardened bars carried in spaced relationshipwith respect to said block, said bars being adapted to guide thereciprocal movement of a filing tool, a work holding block adapted tohold feed dogs in a position with their teeth parallel to said guides,said work holding block having a fiat upper surface for the attachmentof legless feed dogs and also having slots in its side faces for theattachment of feed dogs with extending legs, a rotatable shaft locatedto said work holding block and threadably engaging said base block, alock nut on said shaft for locking the latter against rotation to saidbase block, and guide pins carried by said work holding block andslidably positioned in said block.

LEONARD C. CORCORAN.

